There is a growing demand for energy usage in the United States, primarily due to increasing economic activity. This increasing demand for energy is being met by pursuing increased power generation. Unfortunately, this increase in power generation is resulting in the generation of over 160,000 tons of particulate emissions per year in the United States polluting the air.
Without significant new controls and treatments of emissions, millions of individuals will continue to breathe air polluted by these particulate emissions. Additionally, these emissions will continue to cause damage to environment in the form of acid rain and smog. Significant reductions in emissions of nitrogen oxides (NOx), particulate matter, nonmethane hydrocarbons, carbon monoxide, sulfur dioxide, and other toxins would result in substantial benefits to both the public health and the environment.
At the present time a device that is robust, efficient, durable, packagable, and maintenance-free is not available for elimination of particulate matter. For diesel engines in particular, several devices have been designed to combat the problem of particulate emissions. Most of these devices use different filtration technologies with either thermal regeneration capabilities or manually replaceable filtration media. The problem with these filtration devices is that they quickly clog and increase the exhaust backpressure thus negatively affecting efficiency and performance. In addition thermal regeneration requires vast amounts of energy and produces very high temperatures.
As discussed below, other technologies available for separating particulate matter from a gas stream have been investigated. For example, non-thermal plasma-assisted catalytic reduction of exhaust gases using a corona discharge have been studied and reported in the literature. J. A. Ekchian, E. N. Balles, D. L. Christeller, J. S. Cowart, and W. D. Fuller, “Use of Non-Thermal Plasma Generated by a Corona Discharge Device to Improve the Efficiency of Three-Way Catalyst”, which is herein incorporated by reference in its entirety, disclosed testing on the use of a corona discharge device for the reduction of HC, CO, and NOx in tailpipe emissions in conjunction with a three-way automotive catalyst and reported significant improvements.
Additionally, M. B. Penetrante, R. M. Brusasco, B. T. Merritt, W. J. Pitz and G. E. Wogtlin, “Feasibility of Plasma Aftertreatment for Simultaneous Control of NOx and Particulates”. SAE Paper 1999-01-3637 (1999)”, which is herein incorporated by reference in its entirety, disclosed a study on the feasibility of plasma after treatment of NOx and particulates. This study reported that although NO2 can be used to non-thermally oxidize the carbon fraction of particulates, this does not provide a high level of reduction of NOx since it also leads to conversion of NO to NO2.
Further, Suzanne E. Thomas, Anthony R. Martin, David Raybone, James T. Shawcross, Ka Lok Ng, Phil Beech, and J. Christopher Whitehead., “Non-Thermal Plasma After Treatment of Particulates-Theoretical Limits and Impact on Reactor Design”, SAE Paper 2000-01-1926 (2000), which is herein incorporated by reference in its entirety, disclosed work that was carried out using non-thermal plasma by introducing packing material into the plasma region to increase the residence time for the oxidation of particulate matter in the treatment of diesel exhaust. This reference showed that a non-thermal plasma reactor designed in this manner could be effective in the oxidation of particulate matter at low temperatures. This reference also reported that a two-stage plasma system might be needed to convert NO, produced during the process, back to NO2 upstream of a catalytic treatment. This reference indicated that the plasma in combination with a catalyst would be required to take care of aldehydes and CO.
Unfortunately, each of the technologies still has one or more limitations which prevent it from providing a robust, efficient, durable, packagable, and maintenance-free, particulate trap system and method.